The use of relays to reverse current to a device such as a DC motor, and to provide a closed electrical path to a DC motor, are well-known in the prior art. Examples are given in U.S. Pat. Nos. 3,305,718; 2,755,423; 2,446,299; 1,486,386; 2,587,948 and 2,564,256. All of these patents show a reversable relay which operates to switch contacts and reverse the current to a motor while offering a closed path to the motor when the motor is disconnected from the power supply.
Additionally, U.S. Pat. Nos. 2,446,299; 1,736,683; 2,564,246; and 2,587,948 show a relay having a rocking armature. The rocking motion of the armature forces the making and unmaking of switch contacts.
Further shown is that a set of contacts can be used to reverse a motor as shown in U.S. Pat. No. 2,564,246.
Further shown in U.S. Pat. No. 3,305,718 are a group of relay contacts mounted on separate cantilevered supports which are deflected, forcing the contacts into engagement and disengagement. The contacts control the direction of current through a motor and provide a shorting arrangement to effect dynamic braking.
The prior art shown by these patents indicates numerous attempts to provide a type of reversible relay for use with a reversible current motor, which is effective to provide the necessary contact surfaces and contact force to maintain the current as required to the motor, while offering the advantages of a closed path and dynamic breaking when the motor is deenergized. As indicated above, some of these patents show a rocking type armature arranged over two coils separately energized to cause a pivoting motion of the armature and actuation of the relay.
Cantilevered contacts are shown in U.S. Pat. No. 3,305,718. However, while the electrical arrangements are similar to the other prior art disclosures for reversing current as well as for dynamic braking, switch actuation is accomplished through magnetic fields exerting a force directly on the cantilevered contact support arm.
One of the problems in relays, is the generation of sufficient force to maintain contact, especially where a heavy current is supplied through the contacts, as to an electric motor. A second problem is to provide a relay system which is lightweight and which has a minimum of mechanical parts, enhancing reliability and efficiency. A third problem is to construct a relay so the minimum reluctance is encountered in the flux path, and the magnetic force generated on the armature is maximum for the current provided to the coils. Additionally, relays should be of a construction assuring a minimum of light-weight, easily fitted, parts so that the difficulty and cost of assembly and the intensity of magnetic force required is minimized while the contact force is maximized.